The present invention relates to an machine having plural fixed internal axes with an external rotor and an internal rotor, which are surrounded by a common casing provided on its circumference with an intake and outlet port, the reciprocal engagement of rotors leading to the formation of variable volume working spaces, which are sealed by gap-forming rolling and/or sliding of surface regions of the rotors on one another and on casing faces and the engagement parts of the external rotor extend in axially parallel manner between rotor side parts, over which is mounted the external rotor by means of a bearing surrounding the shaft of the internal rotor.
Apart from the advantage of the rotation of their rotors about fixed axes, machine having plural fixed internal axes have the further advantage that the external rotor can control the intake and outlet passages or ports of the machine in valve-like manner, in that the circumferential surfaces thereof move along the inner face of the casing with a limited spacing forming sealing gaps. Relatively large flow cross-sections are possible. Thus, in principle, such machines are suitable for high rotational speeds of e.g. 40,000 to 50,000 r.p.m., but as a result of the bending of the engagement parts of the external rotor, the known designs only permit an axially short machine construction and large sealing gaps which take account of shape changes, in order to prevent the external rotor running against the inner face of the casing. The throughfeed rate of the known machines is correspondingly low and wide sealing gaps lead to a poor efficiency. In addition, due to thermal expansions, shape changes have a disadvantageous effect, because account must also be taken thereof through adequately wide sealing gaps.